/// <summary>
/// Computes the probability calibration plot for a particular rating value.
/// </summary>
/// <param name="instanceSource">The instance source providing the ground truth.</param>
/// <param name="predictions">A sparse users-by-items matrix of predicted rating distributions.</param>
/// <param name="rating">The rating value to generate the calibration plot for.</param>
/// <param name="bins">The number of bins to use.</param>
/// <returns>The computed probability calibration plot.</returns>
public double[] ProbabilityCalibrationPlot(
TInstanceSource instanceSource,
IDictionary <TUser, IDictionary <TItem, Discrete> > predictions,
int rating,
int bins)
{
IStarRatingInfo <TGroundTruthRating> starRatingInfo = this.mapping.GetRatingInfo(instanceSource);
var countTotal = new int[bins];
var countGuessed = new int[bins];
foreach (var userWithPredictionList in predictions)
{
foreach (var itemPrediction in userWithPredictionList.Value)
{
TUser user = userWithPredictionList.Key;
TItem item = itemPrediction.Key;
double prob = itemPrediction.Value[rating];
int groundTruth = starRatingInfo.ToStarRating(this.mapping.GetRating(instanceSource, user, item));
int probBin = Math.Min((int)(prob * bins), bins - 1);
countTotal[probBin] += 1;
countGuessed[probBin] += (groundTruth == rating) ? 1 : 0;
}
}
return(Util.ArrayInit(bins, i => (double)countGuessed[i] / countTotal[i]));
}
/// <summary>
/// Computes the average of a given rating prediction metric using ground truth in model domain by iterating over
/// <paramref name="predictions"/> and using the aggregation method given in <paramref name="aggregationMethod"/>.
/// </summary>
/// <param name="instanceSource">The instance source providing the ground truth.</param>
/// <param name="predictions">A sparse users-by-items matrix of predicted rating distributions.</param>
/// <param name="metric">The rating prediction metric using ground truth in model domain.</param>
/// <param name="aggregationMethod">A method specifying how metrics are aggregated over all instances.</param>
/// <returns>The computed average of the given rating prediction metric.</returns>
public double ModelDomainRatingPredictionMetric(
TInstanceSource instanceSource,
IDictionary <TUser, IDictionary <TItem, int> > predictions,
Func <int, int, double> metric,
RecommenderMetricAggregationMethod aggregationMethod = RecommenderMetricAggregationMethod.Default)
{
IStarRatingInfo <TGroundTruthRating> starRatingInfo = this.mapping.GetRatingInfo(instanceSource);
Func <TGroundTruthRating, int, double> metricWrapper = (g, p) => metric(starRatingInfo.ToStarRating(g), p);
return(this.RatingPredictionMetric(instanceSource, predictions, metricWrapper, aggregationMethod));
}